Improvement: Make it possible to initialize KVS when snapshot with ID=0 is not available #237

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1. anmittag

   added the

   Epic

   issue type on Feb 9, 2026
2. umaucher

   added

   enhancementNew feature or requestNew feature or request

   on Jul 13, 2026
3. Ahmed-Elsaka-JC commented on Sep 18, 2026

   

   Ahmed-Elsaka-JC

   on Sep 18, 2026

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   for C++ implementation :

   • if kvs_<instance_id>0.json is not available kvs<instance_id>_0.json will be created on first flush

   Is this issue related to C++ implementaion ?
4. arkjedrz commented on Sep 22, 2026

   

   arkjedrz

   on Sep 22, 2026

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   @Ahmed-Elsaka-JC, to start with an answer - I think C++ is affected, because it's not about ::Optional or ::Required behavior. The description of this ticket is misleading.

   I meant that if snapshot with ID=0 is broken, then KVS is not able to initialize. E.g., hash file got removed, or JSON file is malformed.
   Selectable snapshot ID would allow restoring the state using another snapshot - but this would still need a predictable error behavior.
   I dislike the automatic loop idea, especially since IIRC snapshot IDs won't be ordered latest to oldest anymore (planned for #292, but stale).

   Unit tests for Rust exist, but are marked as #[ignore = "Not handled properly yet"] and probably should get revisited and expanded.

   • Both KvsLoad::Required and KvsLoad::Optional should halt on broken snapshot.
     • Regardless if it's a missing file, a malformed one, or an invalid hash.
     • KvsLoad::Optional should be allowed to proceed only if both files are missing.
   • Error handling could be simplified:
     • Merge KvsFileReadError, KvsHashFileReadError and FileNotFound to FileReadError, change description to "File not found or couldn't be read".
     • Merge IntegrityCorrupted and ValidationFailed to IntegrityCorrupted.
   • I'm not sure what should be the behavior for KvsLoad::Optional with added snapshot ID parameter for init. Try load for given ID?
5. Ahmed-Elsaka-JC commented on Sep 23, 2026

   

   Ahmed-Elsaka-JC

   on Sep 23, 2026

   Last edited by Ahmed-Elsaka-JC

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   update :

   From C++ implementation prespective :

   • hash file is missing : -> Failed to open KVS: KVS hash file read error
   • corrupted kvs file format : -> Failed to open KVS: Validation failed

   Fix proposal :

   • provide new parameter called RecoveryPolicy which will be enum as follwoing :
     enum RecoveryPolicy { strict = 0, EmptyFallback = 1, }
   • in case of calling open with stict -> will return the error
   • in case of calling open with EmptyFallback :
     - if hash file is missing or corrupted kvs file , return empty storage .
     - if use still need another storage can call snapshot_restore api to load it.

   ---

   Agreed decision :

   • two recovery approaches :
     1- add another option to OpenNeedKvs (Ignore).
     2- allow user to open another snapshot by passing snapshot number to builder.
6. karolnowak

   self-assigned this

   on Oct 1, 2026
7. umaucher

   closed this as completedin #464on Oct 8, 2026